(a) Field of the invention
The present invention relates to an automatic accompaniment apparatus for electronic musical instruments, which is capable of automatically producing accompaniment tones such as bass tones and arpeggio tones.
(b) Description of the prior art
An automatic accompaniment, in general, means such a performance that accompaniment tones are prepared by circuitries in the instrument upon respective depressions of the keys, and that, thereafter, they are sounded at such timings as required in accordance with the predetermined rhythm to automatically produce, for example, bass tones and arpeggio tones.
As a typical conventional automatic bass accompaniment apparatus, there has been proposed one which is arranged so that, at each time of depression of a chord, a root note data representing the root note of the chord and interval data read out from the memory are, for example, respectively added together to form respective bass key data, and that bass tones are respectively and sequentially produced in accordance with these bass key data. Also, as a typical conventional automatic arpeggio accompaniment apparatus, there has been proposed one which is arranged so that at each time of depression of a chord, depressed key data of the depressed chord (for example C, E, G) are written in the memory, and that the depressed key data requiring sounding are searched successively from the low pitch note side to the high pitch note side, using, as trigger signals, the pulses of a certain period (for example, a time length of a 16th note), and that the depressed key data thus obtained from the search are given an appropriate processing such as an octave processing, to thereby produce arpeggio tones.
The above-mentioned automatic bass accompaniment apparatus and arpeggio accompaniment apparatus are effective for use in a circuit system wherein both the bass tone generation and the arpeggio tone generation are performed in parallel. However, in order to use such apparatuses in a system wherein the bass tone generation and the arpeggio tone generation are processed time-divisionally (i.e. in series), especially in a system wherein they are subjected to time division processing by using a micro-computer, the computation processing requires an undesirably lengthy time, so that there is a drawback in that it is difficult to generate both bass tones and arpeggio tones in synchronism with the selected rhythm. More particularly, in an ordinary electronic musical instrument, chord tones, bass tones, arpeggio tones and so forth should be generated in synchronism with rhythm tones. If, however, an undesirably lengthy time is required for the computation processing intended for the generation of the respective tones, the result is that the bass tones, arpeggio tones and other accompaniment tones undesirably will become generated with delays for the given rhythm timings.
In order to solve these problems mentioned above, there may be used a computer which is capable of performing high-speed computation. However, the incorporation of such a computer in an electronic musical instrument is non-realistic in view of, for example, cost and space.